Unigine::LeapMotion::Hand Struct

Hands are the main entity tracked by the Leap Motion controller. The controller maintains an inner model of the human hand and validates the data from its sensors against this model. This allows the controller to track finger positions even when a finger is not completely visible.

Notice

It is possible for movement or changes in position to be lost when a finger is behind or directly in front of the hand (from the point of view of the controller).

The Leap Motion software matches the internal model against the existing data. In some cases, the software can make an incorrect match – for example, identifying a right hand as a left hand.

This structure represents a physical hand detected by the Leap and provides access to its attributes describing the hand position, orientation, and movement.

The structure has the following set of properties:

ID

ID of the hand.

type

Hand type: 0 - for the left, 0 - for the right one.

witdh

Width of the palm when the hand is in a flat position, in meters.

is_valid

Indicates whether the hand contains valid tracking data (1).

palm_position

Coordinates of the position of the palm.

stabilized_palm_position

Coordinates of the modified palm position with some additional smoothing and stabilization applied.

wrist_position

Coordinates of the position of the wrist.

palm_velocity

Instantaneous velocity of the finger tip, in m/s.

center

Coordinates of the center of the bone.

direction

Normalized direction from the palm position toward the fingers.

basis

Orthonormal basis vectors for this Bone as a Matrix.

Basis vectors specify the orientation of the bone:

X - Perpendicular to the longitudinal axis of the bone; exits the sides of the finger.

Y (or up vector) - Perpendicular to the longitudinal axis of the bone; exits the top and bottom of the finger. More positive in the upward direction.

Z - Aligned with the longitudinal axis of the bone. More positive toward the base of the finger.

The bases provided for the right hand use the right-hand rule; those for the left hand use the left-hand rule. Thus, the positive direction of the x-basis is to the right for the right hand and to the left for the left hand. You can change from right-hand to left-hand rule by multiplying the z basis vector by -1.

You can use the basis vectors for such purposes as measuring complex finger poses and skeletal animation.

Notice

Converting the basis vectors directly into a quaternion representation is not mathematically valid. If you use quaternions, create them from the derived rotation matrix not directly from the bases.